Plasma Assisted Sublimation Process Research Articles

Effect of Ar, O2, and N2 Plasma on the Growth and Composition of Vanadium Oxide Nanostructured Thin Films

AbstractVanadium oxide nanostructured thin films (NTFs) are synthesized using plasma assisted sublimation process (PASP) in different gases' Ar, O2, and N2 plasma (AP, OP, and NP) and O2 gas (OG) ambient. Morphological studies conducted via electron microscopy reveal nanostrips, nanoflakes, nanorods, and nanoparticles organized as clusters for OP, OG, AP, and NP respectively. X‐ray photoelectron spectroscopy (XPS) studies show that samples OP and OG are composed of α‐V2O5, whereas AP and NP are composed of V6O13 along with V2O5. The relative percentages calculated using XPS data show that in AP, V6O13, and V2O5 are 38 and 62%, respectively. These percentages change to 48% for V6O13 and 52% for V2O5 in NP. The V6O13/V2O5 ratio is lower in AP than NP. This increment of V6O13 in NP is due to presence of more reductive species in N2 plasma than Ar plasma. Since N2 plasma contains species like N*, , etc. it leads to the formation of NO2, N2O, etc. Raman spectra indicate the surface of the sample NP consisting of both V6O13 and V2O5, agreeing with the X‐ray diffraction (XRD) and XPS results. Studies demonstrate that plasma ambient during synthesis process affects both morphology and composition of deposited vanadium oxide NTFs.

Plasma assisted synthesis and growth mechanism of rare V2O5 nanostructured thin films

In this communication, the authors have synthesized two rare nanostructures of V2O5 using facile plasma assisted sublimation process (PASP). V2O5 nanoflakes and nanoplates assembled in microspheres (NPMSs) was obtained on large area over nickel coated glass substrate using simple precursor of V2O5 pellets as source of oxide. The temperature of growth is varied along with time duration of deposition in order to obtain the different kinds of nanostructure as well as to understand the role of Ni-seed layer playing in controlling the overall morphology of nanostructures. The morphological, structural, and vibrational properties of V2O5 nanostructured thin films are systematically investigated as a function of time and deposition temperatures. Structural analysis carried out using the XRD shows the pure orthorhombic phase of V2O5 and revealed the dependence of crystallinity on the temperature and duration of growth. The Raman study of vanadium and oxygen atoms in nanostructured thin films (NTFs) is carried out by micro-Raman, which evidences the presence of single orthorhombic phase of V2O5 and accorded with XRD results. HRTEM analysis with SAED confirms that NFs and NPMSs are polycrystalline in nature. The stoichiometry ratio obtained from XPS analysis is ∼2.4, shows the compositional purity and stoichiometric nature of V2O5 NTFs. Based on the observed results a three steps growth mechanism is proposed.

Synthesis of vanadium pentoxide (V2O5) nanobelts with high coverage using plasma assisted PVD approach

Cost-saving, easy-handling, and eco-affable plasma assisted sublimation process (PASP) is proposed to synthesize vanadium pentoxide (V2O5) nanobelts (NBs) with excellent coverage on Si [100] wafer using oxygen plasma without using surfactants/catalysts. Pure orthorhombic V2O5 NBs having average length of few hundred of microns with quite uniform width nearly of 100nm are formed at 500°C. No film is deposited on Si in presence of oxygen gas without exciting plasma at 500°C. HRTEM analysis with SAED pattern confirm that all V2O5 NBs are single crystalline in nature with the fringe width of 0.33nm corresponding to [010] crystal plane. The XPS analysis shows the compositional purity and sub-stoichiometric nature of V2O5 NBs. The sub-stoichiometric nature of NBs is manifested through an appearance of low intensity peak corresponding to low oxidation state of V (i.e. V4+) at the binding energy of 514.8eV. The micro-Raman and FTIR analysis of NBs are carried out to study the different vibrational modes exhibited by V and O atoms coordinated in distinct fashions. The nanobelts exhibit room temperature PL emission in UV–visible realm with a broad hump in the range of 450–750nm, which confirms the presence of oxygen defects in NBs and strongly supports the XPS results as well. The possible growth mechanism of α-V2O5 NBs is proposed in this paper briefly.

Effect of substrates on the growth of α-MoO3 nanostructures via plasma assisted sublimation process

In this communication, we have investigated the substrate effect on the growth of MoO3 nanostructured thin films prepared by plasma assisted sublimation process (PASP). Three different substrates viz. ITO glass, Ni/Si [100], and Ni/glass are used in deposition process. The surface analysis endorsed that Ni/Si and Ni/glass substrates are most favorable for the uniform growth of vertically aligned MoO3 nanoplates (NPs) and nanoflakes (NFs) of well controlled features with very high aspect ratio (height/thickness) >30, whereas nanostructure formed on ITO/glass substrate is improper (in terms of features and alignment). The X-ray diffractograms divulge that MoO3 films deposited on all substrates exhibit pure orthorhombic phase with preferential crystallographic orientation along [110] direction particularly in case of Ni/Si and Ni/glass substrates. Atomic force microscopic analysis reveals that the average substrates roughness enhanced in presence of pre-deposited layer and monitor the growth of nanostructures. High resolution transmission electron microscopic analysis with selected area diffraction pattern confirmed that both the MoO3 NPs and NFs are single crystalline in nature. The Raman and IR spectrum of all films further endorse the presence of single orthorhombic phase in accordance with the XRD results and also confirm the effect of nanosize on the vibrational properties.